Abrasively immobilised multiwalled carbon nanotube agglomerates: A novel electrode material approach for the analytical sensing of pH

Agglomerates of multiwalled carbon nanotubes (MWCNTs) can be formed in which the binder in the agglomerate is itself a redox active mol. solid. Two sep. agglomerates were formed by dissolving 9,10-phenanthraquinone (PAQ) or 1,2-naphthaquinone (NQ) in acetone together with MWCNTs and adding an excess of aq. soln. to cause pptn. of agglomerates, ~10 µm in dimension, which consist of bundles of nanotubes running into and throughout the amorphous mol. solid that binds the agglomerate together. The nature of this structure, when immobilized on a substrate electrode and in contact with aq. electrolyte solns. gives rise to many three-phase boundaries, electrolyte|agglomerate|conductor, which is advantageous to the solid state anal. electrochem. of such a material as it imparts a larger electroactive surface area than other modified carbon electrodes. The two agglomerates each gave a voltammetrically measurable response to changes in pH; when abrasively immobilized on a basal plane pyrolytic graphite electrode a plot of peak potential against pH produced a linear response for both MWCNT-PAQ and MWCNT-NQ agglomerates over the pH range pH 1-12 and over the temp. range 20-70 C. [on SciFinder(R)]